1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to providing a quality of service (QoS) of audio and video (AV) streams, and more particularly, to providing a QoS of AV streams, in which a period for processing AV streams is separately assigned at a predetermined time in order to process data to provide the QoS, and a plurality of AV streams are simultaneously processed.
2. Description of the Related Art
A carrier sense multiple access with collision detection (hereinafter, referred to as “CSMA/CD”) algorithm is an Ethernet transmission protocol that has been standardized in the IEEE 802.3 standard. According to the CSMA/CD, each of the medium access units (MAUs) connected to Ethernet, monitors whether the line they are commonly connected to is in use, and transmits data when the line is not in use.
If one MAU starts data transmission when another MAU is transmitting data, a collision occurs. Thus, this data is discarded, and the MAU of the receiving party requests that the MAU of the transmitting party retransmit the data. Each of the MAUs waits for a certain time period and retransmits the data a predetermined number of times until data transmission is successfully completed.
A hub or a router may be used to relay data.
At present, IEEE 802.3 Ethernet is the most widely used network technology. IEEE 802.3 Ethernet uses the aforementioned CSMA/CD algorithm as a medium access control (MAC) layer protocol. This is to make the MAC structure as concise as possible. The MAC layer processes traffic in a best effort mode that depends on free competition of traffic when assigning bandwidth.
The performance of such Ethernet improves as switching routers improve. In other words, a half-duplex communication mode, in which competition between channels is made in a related art hub or repeater has been changed to a full-duplex communication mode by the switching router. Thus, each host connected to the router uses all the bandwidth assigned to a port of each channel.
For reference, the switching router is referred to as a layer 2 switch or a wire-speed router Ethernet switch. In the present invention, the switching router is referred to as a switch.
FIG. 1 is a conceptual view illustrating the construction of a related art switching hub. Referring to FIG. 1, the related art switching router includes an input port 11, an output port 12, and a buffer 13.
A port that serves to input and output data, as shown in FIG. 1, is divided into input ports 11 and an output ports 12. That is, the port performs input or output functions.
In FIG. 1, a four-port switching router is shown. Data input to each input port 11 is output through a predetermined output port 12. At this time, since the port performs one of input and output functions, input and output functions cannot be performed simultaneously through the same port. For example, data input to a first port 11a should be output through second, third and fourth ports 12b, 12c and 12d. That is, data transmission cannot be performed through a crossing point between the input port 11 and the output port 12 formed by the same port in FIG. 1.
Data input through the input ports 11 may temporarily be stored in buffers 13 assigned to the output ports. The buffer 13 operates in a first in first out (FIFO) manner. For example, the data transmitted from a plurality of input ports 11 is sequentially output through the output ports 12. The data output through the output port 12, i.e., the data input through the input ports 11 could be simultaneously input to the buffer 13. The buffers may be provided at each input port 11 or at the crossing point between the input ports 11 and the output ports 12.
The related art router or switching hub regards data relating to a request for a QoS as general data. For this reason, if data relating to a request for the QoS to a port whose bandwidth has been exceeded is input, the related art router or switching hub discards the data and the QoS is not provided. For example, when AV streams are processed through specific ports, if file transmission is performed through the same port, the AV streams may be disconnected due to the contention.
FIG. 2 is a conceptual view showing how traffic is processed by a related art hub. Referring to FIG. 2, AV streams are input through a first input port 21a, and the input data is output through a fourth output port 22.
At this time, general data is input to a second input port 21b and a third input port 21c, and the input data is output through the fourth output port 22. In this case, if the capacity of a buffer 23 of the fourth output port 22 is exceeded, the data from each input port competes with one another in the fourth output port 22. Thus, some of the AV streams may not be output. Also, most of the general data occupies the maximum bandwidth during data transmission because of best effort characteristics. Therefore, the AV streams transmitted at uniform bandwidths may be damaged by the general data.
In case of general data, some of data that is not output may be processed through retransmission. However, in case of AV streams, data that is not processed cannot be processed again due to a time limit. If traffic requiring a QoS, such as AV streams, is generated, a router that provides the QoS is required.
US Patent Publication Number 2003-0007724 discloses a system and method for processing data input to a buffer of an optical node provided between a hub and a user using a time division multiple access (TDMA) mode to provide input and output functions of a video file. However, this publication fails to disclose the processing of a plurality of input data.